There is a wide variety of adhesive compositions currently available for bonding elastomeric materials to metal surfaces. Many of these adhesive compositions utilize various halogenated polymers to provide the adhesive compositions with film-forming capability, enhanced adhesion, and resistance to adverse environmental conditions. One of the most common and most effective halogenated polymeric materials is chlorinated natural rubber or chlorinated synthetic rubber such as chlorinated polyisoprene. The chlorinated natural and synthetic rubbers have been found to provide excellent film-forming properties, adhesional affinity for both metal surfaces and vulcanizing elastomers, and environmental resistance when utilized in adhesive compositions for bonding elastomeric materials to metal surfaces.
The process for preparing the chlorinated rubber materials traditionally employed in adhesive compositions typically involves the utilization of highly chlorinated solvents such as carbon tetrachloride. The increasing number of environmental regulations relating to chlorinated solvents has limited the availability and usability of many chlorinated solvents. In fact, the utilization of chlorinated solvents in industry may become totally prohibited in the very near future.
Processes for preparing chlorinated rubber materials which do not utilize chlorinated solvents are therefore currently being explored. However, a process has yet to be developed which produces chlorinated rubber materials equivalent to the materials produced by a process based on chlorinated solvents such as carbon tetrachloride. Therefore, the adhesive industry is searching for materials which can be prepared without the utilization of chlorinated solvents and which can act as an effective substitute for the traditional chlorinated rubber materials.
Chlorinated polyolefins, such as chlorinated polyethylene, can be prepared without the utilization of chlorinated solvents and have previously been considered for utilization in rubber-to-metal adhesive compositions as alternatives to chlorinated rubber materials. Chlorinated polyolefins, however, have traditionally not provided adequate metal-wetting capability or environmental resistance so as to be effective for use in rubber-to-metal adhesive compositions.
A need therefore exists for a chlorinated polymeric material which can be prepared without the utilization of chlorinated solvents and which can be utilized as an effective substitute for the traditional chlorinated rubber materials.